Examples of radiographic apparatus that obtain fluoroscopic images of a subject includes one in which a radiation source irradiates the subject with radiation beams in a cone shape, and a flat panel detector (hereinafter, abbreviated as “FPD”) detects radiation that transmits through the subject. In such radiographic apparatus, scattered radiation occurs that scatters inside the subject in transmitting therethrough and enters into the FPD, which leads to a lower contrast fluoroscopic image of the subject, in order to prevent scattered radiation from entering into the FPD, a radiation grid may be provided that covers a radiation detection surface of the FPD.
Now, description will be given of a construction of a conventional radiation grid. As shown in FIG. 20, the conventional radiation grid 71 includes strip absorbing foil strips 72 composed of a molybdenum alloy etc., that readily absorb radiation, and spacers 73 that support them and maintain its linear shape. The absorbing foil strips 72 and spacers 73 are arranged alternately to form a plate absorber. In the radiation grid 71, direct radiation traveling through the subject passes through the gap 72 between the adjacent absorbing foil strips 72 (spacer 73, to be exact), whereas scattered radiation enters into the absorbing foil strips 72, where it is absorbed.
For obtaining clearer fluoroscopic images, it is desirable not to provide the spacers 73 that obstruct travel of direct radiation. Accordingly, a radiation air grid has been developed having no spacer 73 in recent years (see, for example, Patent Literature 1.) Here, description will be given of a construction of a conventional radiation air grid. As shown in FIG. 21, the conventional radiation air grid 81 has a pair of seat covers 85, 86 that covers an absorber 84. The radiation air grid 81 has no spacer. Thus, each of absorbing foil strips 82 is fixed through adhesion to the seat covers 85, 86.
However, only the seat covers 85, 86 cannot sufficiently support the absorbing foil strips 72. Accordingly, the absorber 84 is mechanically brittle. Consequently, in the conventional radiation air grid, the adhesive 87 penetrates side ends of the absorber 84, thereby enhancing mechanical strength of the absorber 84. For manufacture of such radiation air grid 81, two or more absorbing foil strips 82 are arranged parallel to one another. The adhesive 87 is applied so as to cover each end of the absorbing foil strips while a tension is applied to each of them, whereby the adhesive 87 penetrates the gaps between the adjacent absorbing foil strips 82. Upon curing of the adhesive 87, the seat covers 85, 86 having the adhesive 87 applied thereto cover the absorber 84, and the absorbing foil strips 82 are cut off at both ends thereof to have an even length. Accordingly, the radiation air grid 81 is to be manufactured.    [Patent Literature 1] U.S. Pat. No. 7,072,446